I am very confident on source - they come from Burma direct to Singapore, bypassing TH and JJ Market. There is very strong direct capital flow beetween SG and MM, mostly due to bad blood (as you well aware) spilled beetween Burma and Thailand (say Hi to never defeated Thai kingdom hahaha).

They come with other stuff that gets digged from the ground - mostly votive tablets, some pottery and etc... On dating they NOT all Pyu ( i have 0 interest to use world "tircut" as it not used by anyone here), some of them come from Bagan period. Its easy to tell by some other stuff that comes with them.

There are 2 possiblitis:
1. uncleaned and unwashed. Most small beads have very diffrent color from beads your posted. I.e. they are not cleaned and washed and treated. Color of gold is very different from one on your picture and picture from moscitobay. That makes it easy spot.
2. cleaned and washed. They have same color and same patina (lack of patina) as on pictures from you and moscitobay. They mostly come from JJ Market and TH, it makes it harder to tell, so i am trying not to buy them, unless i absolutley trust the source.

Cheers
Tofsla