Romania has a 15 day visa on arrival for 2,000 THB. This visa on arrival can NOT be extended, and a new visa CAN NOT be purchased inside Thailand.
OVERSTAYING is a crime. The fine for overstaying is 500 THB a day with a maximum fine of 20K THB. If he is caught while on overstay, he will be blacklisted. See
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[Thai Youtube Video]
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For the punishments.
He should enter on a single entry tourist visa