@Kanyarat *************
I recommend simply requesting a 60 day extension of stay based on unable to travel due to COVID-19 so he can get off of the overstay.
Going from a 60 day extension of stay based on unable to travel due to COVID-19 to a one year extension of stay based on employment will be between him and the employer.
1. Your passport and:
a. a copy of your data ("picture") page
b. a copy of your most recent visa (if you have one)
c. a copy of your most recent stamp
d. a copy of your departure card
2. [MAY NOT ALWAYS BE REQUESTED] A TM30, filed in the immigration office.
3. The forms (each immigration office may have different forms, and ant to use their special forms)
4. A letter from your embassy saying you can not return, OR a print out from your embassy website saying they donβt issue the letters, OR a print out of a letter from the embassy saying they don't issue those letters.
5. 2x passport pictures
6. 1,900 THB.
The fine is 500 THB a day for being on overstay.