If his passport is expired he is on overstay
Did my US passport renewal last Dec , Its all done online an not difficult to do ( unlike the UK one)
took 41 days from the day i sent it in, till i got it back
if it has been submitted there is a link to check status
https://passportstatus.state.gov/
I have seen agents advertising to arrange the passport for around 20,000 baht
a total waste of money in my eyes
once he gets new one back, buy a ticket out of thailand, pay the overstay and return on a visa exempt and start the non o over. WITH a Different agent!!!