Thailand has a 7% value-added tax (VAT) on many goods and services. Midrange and top-end hotels and restaurants might also add a 10% service tax. When the two are combined this becomes the 17% hit known as ‘plus plus’, or ‘++’.
You can get a refund on VAT paid on shopping, though not on food or hotels, as you leave the country. For how-to info, visit www.rd.go.th.