There were Straits Settlements stamps used in Bangkok in Siam (now Thailand) with ‘B’ overprints, and sometimes with surcharges, in the 1880s by Great Britain.
The catalog value of these stamps, of which there are several variations, colors, and denominations (in decimalized dollars and cents), is often much higher than what the stamps are actually sold for. This is in part due to the number of convincing counterfeits that have unfortunately been introduced into the marketplace over the years.
At any rate, the stamps are an interesting and somewhat postally obscure slice of Siamese and British history, and can be highly collectible; check the current selection of Bangkok overprinted Straits Settlements stamps for sale. The listings are refreshed every day.
