@Paul *******
I'd delete this, you are very wrong.
If he wants a multiple re-entry permit, to leave and return, that would be stupid to do on 90 days.
He should/could get the single re-entry if he want to leave and comeback in the 90 days.
If he in fact wants a multi-entry Visa obtained at an Embassy outside of Thailand, he would them have to leave every 90 days of the duration of the visa.
2 entirely different things.
Although if the terms not used correctly can be very confusing.