What Qualifies As A Revenue Stamp?

Even after collecting Thailand revenue stamps for 25++ years, I am still sometime confused what qualifies as a revenue.
I will give a sample below.
The Thailand document is a permission or license to operate a HAM radio in 1938.
In the top right is a label or stamp with some serial number written inside.
I am sure money had to be paid to acquire this license.
The label/ stamp is not listed anywhere.
So what is it, label or revenue? Please give me your thoughts on this.
Thanks

The label reads: Post and telegraph department number 10/481

Could be it was just a label showing the document was registered and sealed by the Siam post.

The UPU requires that postage stamps have an express face value; I'd imagine any definition of revenue stamp would have something similar. So, since this sticker has no value printed or written upon it, it's not a revenue stamp, and is indeed a label.

Revenue stamps would normally have a value either in money or in product quantity; however if all radios were treated equally and a fee was identical in all cases it might not necessarily have one. More research is needed.

The FIP definition of a revenue includes: (1) shows payment of a fee or tax or that the object is exempt from a tax, (2) shows that one has a credit with the government, or (3) pays a fee for a government service. In much of my writing about the definition of revenues I have amplified this last category to include registrations or license fees. So I would include your example as a revenue stamp. Just because it does not appear in a Thai revenue catalog, should not be interpreted as it is not a revenue. In fact the Scott U.S.Specialized lists less than half the federal revenue stamps.

Parenthetically, one should note that the last category probably includes postage stamps, as they pay a fee for a government service. So, postage stamps are simply a subcategory of revenue stamps!!

Thanks revenuermd.

The stamp on the document and the loose stamp have the logo of the Post and Telegraph department of Thailand. Can the post department be considered a government department?

Also as separate question, are airport departure fee receipts or stamps also considered as revenue stamps?

Jossanders52. Airport departure fees payable with stamps are certainly revenues. In every case I know, there is an agency created by legislation of some sort that gives the "taxing" authority to these agencies. Here in the US I believe these agencies are referred to as airport authorities.

Hi Jos,
I would direct enquiries here, for possible ID

https://www.qsl.net/rast/text/licensing2016.html

Email address: hs1fvl(AT)gmail.com

Thanks Rod,
will contact them for more info.