The trouble with "trader" is that it usually means something else, namely someone who trades. A tradesperson doesn't trade; they practise a trade (= craft/profession).
Visit a UK builders' merchant or DIY store and they'll offer a 'trade account' with a 'trade discount' and 'trade deals' - they'll even sell you 'trade paint'
Ambiguous on a global scale? Maybe. Ambiguous when you're standing in a builders' merchant? Absolutely not.
The term seems to lack gender-neutrality so Wikipedia prefers: https://en.wikipedia.org/wiki/Tradesperson
The trouble with "trader" is that it usually means something else, namely someone who trades. A tradesperson doesn't trade; they practise a trade (= craft/profession).