Actually they cannot tax your guitar. If they were, then they'll have to tax all your personal belongings like your toothbrush that you're having on you.

Maybe some greedy officers just pretend to stop you so they can get some duit kopi

I really don't know what's the confusion that you guys are having...LOL

I bought:-
Fender Strat and Mustang from US - no tax
my Big baby from Singapore using train - no tax
Gibson SG from Singapore using train - no tax
most recently a Martin D-16GT acoustic - no tax

so did someone here actually got taxed for a guitar? As far as I know, legally speaking, no tax, but if you were to be shipping like 10 guitars then maybe( I'm not sure) you'll get tackx.