Btw immigration officer has been quite suspicious asking many questions about my situation in Thailand and checking my very basic level of Thai (since I have been staying with an ED visa). At the end he told me "you are not a tourist, I cannot stamp your visa", I had to explain very calmly since I am not working I can only be a tourist, and showing my mandatory return ticket to get my visa in Phnom Penh finally convinced him to stamp my visa...
No harm done, just 5 or 10min at the immigration counter much more stressful than usual. 🙏