At the commencement of each day after the first day, a witness may demand his fees for that day's attendance in obedience to a subpoena; and if the same be not paid, he shall not be required to remain, except witnesses subpoenaed by any state department, board, commission or legislative committee authorized by law to issue subpoenas shall be paid for their attendance and necessary travel as provided by law in other cases at the time their testimony is completed.
Okla. Stat. tit. 12, § 400