20 Baht

P#88 sits in an interesting transitional moment for Thai currency printing. Thomas De La Rue had held the Bank of Thailand contract for decades by this point, and the 1981 series represented one of the last major issues before Thailand began diversifying toward domestic and alternative foreign printers in the 1990s. The watermark — a single security feature by the standards of the period — reflects pre-digital assumptions about forgery risk that the Bank of Thailand would substantially revise in subsequent series.