He doesn't have to fill anything out. In fact, he could stay twice as long(60 days) on just his passport that you say is no longer mighty. Lol. In fact, the Thai government has big concerns of losing lots of tourism from the West due to the Baht being stronger against the USD than it normally is(worst exchange rate since 19 months ago). 👍
Currently he'll want to go back when he sees the exchange rate in Thailand after being in the PH w/the 56 pesos to $1USD rate. But he'll definitely want to come back when the Baht weakens later(and it will eventually)