From the Royal Thai Embassy - Phnom Penh Facebook page:
"The Royal Thai Embassy in Phnom Penh will adopt the e-Visa application on 8th October 2024.
Last day of walk-in application: October 4th, 2024. Not much time left...
TLDR : Answer Summary
The Royal Thai Embassy in Phnom Penh will switch to an e-Visa application system starting October 8, 2024, with the last day for walk-in applications being October 4, 2024. There are questions regarding the applicability of this new system, particularly whether it covers Non B visas in addition to DTVS, and some believe this applies only to applicants from Cambodia.