Is it normal for my package to sit in Bangkok for a week after shipping?

Parcel By Air takes around 1 month to arrive, and yes, it means long processing time at every processing center, as they consolidate shipments by routes and send them out,say, weekly. Also, events are often entered retrospectively, i.e. may be parcel had left already on Friday, and it will be entered on Monday in a sysrem.

Net time of movement by air is quite short, but usually going through few hubs with processing time in each of it.

Over the land parcels take ca.2 months to arrive - in contrast.

It's possible it has already left Bangkok and is between mail systems, the next notification may be when it arrives with USPS.

Usually though I do see "SUVARNABHUMI MAIL CENTRE" after "Bangkok EMS Centre", then that's the last one before the destination carrier.

Depends on what you sent.

Waiting on customs most likely