this is what i do the cost
0.20 USD x 33 bht = 6.6 bht
6.6 x 11-20% for shipping = 7.32-7.92
if you want to do proper tax around 30-40%
7.32 -7.92 x 40% = 10.24- 11.08 bht
if you want to save cost you can order 2 lots, one lot order with HS code ( tax)
2nd lot order with no tax then the cost can be average
that's the general cost.
after that is your mark up and cost for your space to put at the shelf