SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 4)

NATURAL GAS SERVICES GROUP INC

(Name of Issuer)

Common Stock, par value $0.01 per share

(Title of Class of Securities)

63886Q109

(CUSIP Number)

Hoak Public Equities, L.P.
3963 Maple Avenue, Suite 450,
Dallas, TX, 75219
(214) 855-2284

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

01/05/2026

(Date of Event Which Requires Filing of This Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box. Checkbox not checked

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

SCHEDULE 13D

CUSIP No.

63886Q109

Name of reporting person

Hoak Public Equities, LP

Check the appropriate box if a member of a Group (See Instructions)

(a)

(b)

SEC use only

Source of funds (See Instructions)

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

Checkbox not checked

Citizenship or place of organization

TEXAS

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 838,128.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 838,128.00
10	Shared Dispositive Power 0.00

Aggregate amount beneficially owned by each reporting person

838,128.00

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in Row (11)

6.67 %

Type of Reporting Person (See Instructions)

Comment for Type of Reporting Person:

The item (13) calculation is based on 12,568,917 shares of Common Stock of the Issuer outstanding as of November 7, 2025, as disclosed on the Issuer's Form 10-Q filed with the SEC on November 10, 2025.

SCHEDULE 13D

CUSIP No.

63886Q109

Name of reporting person

Hoak Fund Management, L.P.

Check the appropriate box if a member of a Group (See Instructions)

(a)

(b)

SEC use only

Source of funds (See Instructions)

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

Checkbox not checked

Citizenship or place of organization

TEXAS

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 838,128.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 838,128.00
10	Shared Dispositive Power 0.00

Aggregate amount beneficially owned by each reporting person

838,128.00

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in Row (11)

6.67 %

Type of Reporting Person (See Instructions)

Comment for Type of Reporting Person:

SCHEDULE 13D

CUSIP No.

63886Q109

Name of reporting person

Hoak & Co.

Check the appropriate box if a member of a Group (See Instructions)

(a)

(b)

SEC use only

Source of funds (See Instructions)

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

Checkbox not checked

Citizenship or place of organization

TEXAS

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 838,128.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 838,128.00
10	Shared Dispositive Power 0.00

Aggregate amount beneficially owned by each reporting person

838,128.00

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in Row (11)

6.67 %

Type of Reporting Person (See Instructions)

Comment for Type of Reporting Person:

SCHEDULE 13D

CUSIP No.

63886Q109

Name of reporting person

Hoak J. Hale

Check the appropriate box if a member of a Group (See Instructions)

(a)

(b)

SEC use only

Source of funds (See Instructions)

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

Checkbox not checked

Citizenship or place of organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 838,128.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 838,128.00
10	Shared Dispositive Power 0.00

Aggregate amount beneficially owned by each reporting person

838,128.00

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in Row (11)

6.67 %

Type of Reporting Person (See Instructions)

Comment for Type of Reporting Person:

SCHEDULE 13D

CUSIP No.

63886Q109

Name of reporting person

HOAK JAMES M

Check the appropriate box if a member of a Group (See Instructions)

(a)

(b)

SEC use only

Source of funds (See Instructions)

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

Checkbox not checked

Citizenship or place of organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 838,128.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 838,128.00
10	Shared Dispositive Power 0.00

Aggregate amount beneficially owned by each reporting person

838,128.00

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in Row (11)

6.67 %

Type of Reporting Person (See Instructions)

Comment for Type of Reporting Person:

SCHEDULE 13D

Item 1.

Security and Issuer

(a)

Title of Class of Securities:

Common Stock, par value $0.01 per share

(b)

Name of Issuer:

NATURAL GAS SERVICES GROUP INC

(c)

Address of Issuer's Principal Executive Offices:

404 VETERANS AIRPARK LANE, SUITE 300, Midland, TEXAS , 79705.

Item 1 Comment:

This Amendment No. 4 to Schedule 13D ("Amendment No. 4") amends and supplements the Schedule 13D originally filed with the Securities and Exchange Commission ("SEC") on November 28, 2022 (the "Original 13D") and Amendment No. 1 to the statement on Schedule 13D filed with the Securities and Exchange Commission on December 9, 2022 ("Amendment No. 1") and Amendment No. 2 to the statement on Schedule 13D filed with the Securities and Exchange Commission on December 30, 2022 ("Amendment No. 2") and Amendment No. 3 to the statement on Schedule 13D filed with the Securities and Exchange Commission on January 11, 2023 ("Amendment No. 3" and together with the Original 13D, Amendment No. 1, Amendment No. 2, Amendment No. 3 and this Amendment No. 4., the "Schedule 13D"). Unless otherwise indicated, all capitalized terms used but not defined herein shall have the same meaning ascribed to them in the Original 13D. This Amendment No. 4 is being filed to make amendments to the Schedule 13D as follows:

Item 3.

Source and Amount of Funds or Other Consideration

Item 3 is hereby amended and restated to read in its entirety as follows: "The total amount of funds used for the purchase of Common Stock by HPE was $13,427,930.38. All of the shares of Common Stock beneficially owned by HPE were paid for using working capital of HPE. Hoak Management does not directly hold any Common Stock but may be deemed to beneficially own the Common Stock owned by HPE. The other Reporting Persons do not hold shares of Common Stock directly but may be deemed to beneficially own the Common Stock owned by HPE."

Item 5.

Interest in Securities of the Issuer

(a)

Item 5(a) is hereby amended and restated to read in its entirety as follows: (a) As of the date of this Schedule 13D, based upon 12,568,917 shares of Common Stock outstanding (as disclosed on the Issuer's Form 10-Q filed with the SEC November 10, 2025): (a) HPE directly owns an aggregate of 838,128 shares of Common Stock, representing approximately 6.67% of the outstanding Common Stock; (b) Hoak Management, in its capacity as HPE's general partner, may be deemed to beneficially own an aggregate of 838,128 shares of Common Stock, representing approximately 6.67% of the outstanding Common Stock; and (c) each of Hoak and Co. (in its capacity as the general partner of Hoak Management), James M. Hoak (in his capacity as Hoak & Co.'s controlling shareholder), and J. Hale Hoak (in his capacity as Hoak & Co.'s President) may be deemed to beneficially own an aggregate of 838,128 shares of Common Stock, representing approximately 6.67% of the outstanding Common Stock."

(c)

Item 5(c) is hereby amended and restated to read in its entirety as follows: Schedule A hereto sets forth all transactions in the Common Stock within the past 60 days by any Reporting Person. All such transactions were effected on the open market. Except for the transactions set forth on Schedule A, none of the Reporting Persons effected any transaction in the Common Stock during the past 60 days.

Item 7.

Material to be Filed as Exhibits.

99.1 Joint Filing Agreement dated January 7, 2026, by and among Hoak Public Equities, L.P., Hoak Fund Management, L.P., Hoak & Co., James M. Hoak and J. Hale Hoak. 99.2 Schedule A - all transactions in the Common Stock within the past 60 days by any Reporting Person.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Hoak Public Equities, LP

Signature:	/s/ J. Hale Hoak
Name/Title:	J. Hale Hoak, President (Hoak & Co., its general partner)
Date:	01/07/2026

Hoak Fund Management, L.P.

Signature:	/s/ J. Hale Hoak
Name/Title:	J. Hale Hoak, President (Hoak & Co., its general partner)
Date:	01/07/2026

Hoak & Co.

Signature:	/s/ J. Hale Hoak
Name/Title:	J. Hale Hoak, President
Date:	01/07/2026

Hoak J. Hale

Signature:	/s/ J. Hale Hoak
Name/Title:	J. Hale Hoak
Date:	01/07/2026

HOAK JAMES M

Signature:	/s/ James M. Hoak
Name/Title:	James M. Hoak
Date:	01/07/2026

Amendment: SEC Form SCHEDULE 13D/A filed by Natural Gas Services Group Inc.