Addressed: to A. Matters? present in Bangkok.

Gary Wayne Loew, FRPSL suggested that the name might be “Mathiews”.
A search of the 1885 and 1888 Directories as well as the Siam Weekly Advertiser newspaper yielded no listing under this name.
I then tried "Mathews" with the same results.
Maybe there is other addressed mail to him yet to be discovered.
[1 Feb 2026]

Message:
Siam - Bangkok
Feb 3 1885 or 1887
Dear Sir, 

The USA signed a treaty with Siam on 29 May 1856.
They operated a Consulate which was elevated to a Legation on 23 October 1882.
The handwritten date on the reverse must be after this date.

The last digit is not a three when compared with the three to the left. It does not look like a 4. So, the date is most likely 3 February 1885 or 1887.

It is signed with what looks like "A.M." who was most likely a clerk at the Legation.

The use of a Hong Kong postal stationery card seems to have been by convenience - it might have been what was available to send the note.  It most certainly did not go through the Siamese Post Office operating in Bangkok otherwise there would be a Siamese Post Office cancellation. I assume that it was carried by a messenger from the US Legation.

Source:  Santi Siritaweechai June 2022 - thanks!

•   J.E. is likely an owner’s initials.
• The vertical TT on the right side at the bottom is the mark of Max Their of Berlin, a worldwide expert active 1890 to 1920. He used a German “TT” on used stamps and a single “T” on mint or mint no gum stamps. In this position it indicates that this is a genuine B-overprinted stamp.
• The pencil markings are indecipherable.

This is a Siamese postal stationery card only valid for use within Siam. They show that an agreement existed between the Postmaster at the Consulate and the firm of Ramsay & Co. to receive notices as to when the foreign mails would close. See Mail Closure Notices on the home page.

The CDS on the reverse is there to note the date of mailing. However, someone at the British Post Office cancelled the card front which they had no authority to. The mail system in Bangkok was the responsibility of the Siamese Post Office. Note the Siamese cancellation.

On pages 101 & 102 of the book I note three occasions where this error has been seen. One is on this loose Siamese stamp cancelled 27 of an unknown month in 1884. The two other examples are Ramsay & Co. cards cancelled: 15 SP 1884 and 18 NO 1884.

Why did this occur? Maybe an experiences helper was aiding the Postmaster or maybe filling in for him. We will likely never know.

[GROSVENOR #139 22-23 January 2021 Lot 928]