How Siam escaped annexation

In a letter about how Old Siam preserved its independence in the latter part of 19th century, Prasan Stiangrapapongs wrote “It was Russia’s Tsar Nicolas II who saved Thailand from being colonised by Great Britain and France.” 
Certainly.Khun Sanan was privileged enough to have had access to some secret documents proving once for ever that Thailand owes its independence thanks to the Russian government at that time.
That is why I look forward to that document to be published by The Nation, thanks to Khun Prasan’s kindness. 
However, both Great Britain and France, then both paramount powers in that part of the world, came to the conclusion that an independent Siam between their respective colonial empires was the best solution to avoid a harmful conflict between themselves, while imperial Germany was getting more and more powerful in Europe at that time.
Thus, the joint Anglo-French declaration of January 15, 1896, in London, signed by Lord Salisbury, British Secretary of Foreign Affairs and the Baron de Courcel, French Ambassador in London, which specifically stated that both countries guaranteed the independence of The Kingdom of Siam.
Without that joint engagement, it is obvious, indeed, that one or even both powers would have sooner or later attempted to annex Siam to their respective empire.
Michel Muscadier