Had some questions about USM airport in general was hoping those more experienced can help provide some information.

1) Having never been to USM before, how large is the airport, and how efficient is it? Ie. How early before my flight should I plan to arrive (w/ checked bags).
2) How reliable/on-time are PG flights to/from USM and BKK? I'm self connecting at BKK, with BKK international departure at 8pm. Looks like there are tons of options between USM-BKK, was considering either the 1pm or 2:15pm arrival. Assuming typical operations, how risky is this plan? Traveling in May, if time of year makes a difference.