Pest Pro said chemicals are definitely required. They are fine to restrict to just one room, at the (obvious) risk of missing the bugs in other rooms.

Blk 177 furniture shop has low-cost pesticide $18/bottle. The owner said need to spray once a week for a few weeks to kill all the newly hatched bugs.

Dr Yii (Raffles Medical) said — In his army days, if bed bug found, soldiers put the mattress/bed out in the sun from morning to evening. Just once. Bed bugs would never show up again. This is experience, not science.