Current Thai labour law is max 48 hour week @ 8 hrs per day.
you really think they will revise it to 4 days ?
FWIW the company I am at works 5 days at 9 hours (1 hour overtime every day for production staff).
For production staff Saturdays are mandatory @ 9 hours paid as overtime.
We also work two shifts open 24/7, every hour over the 5x9 are paid at overtime penalties (with paid meal breaks).
Many companies in the same industrial area do the same, we are but one of many industrial area's on the Eastern Seaboard that employ millions.