Yes. Best times to arrive in BKK would be before 12pm, and after 7pm.
Having said that, arriving at HKT (Phuket) on a weekday at 3pm was fine. No queue at immigration. Arrived on a Saturday , same time and it was pandemonium ! With three flights from Russia, China and HK, the immigration hall was a zoo with no queueing and no order.
Never again !