17 Sir Henry Gullett, Minister for External Affairs, to Mr R. G. Menzies, Prime Minister
Letter CANBERRA, 15 January 1940
[R. G. Casey, Minister for Supply and Development, visited Thailand in December 1939 while returning from his mission to London. On 21 December he wrote to Menzies and Gullett to report that the U.K. Minister in Bangkok, Sir Josiah Crosby, 'would welcome any move that would make the presence of Australia felt to a greater degree in Siam, and that to this end Crosby had suggested that if Australia should open a legation in Japan or China the Australian Minister might also be accredited to the Thai Government. Casey explained the efforts being made by Japan to wean Thailand away from friendship with Britain and France and the interest of the latter two countries in concluding a non- aggression pact with Thailand. France was, however, reluctant to make the concessions of border areas of Indo-China which the Thai authorities made a precondition of concluding a pact with France.
Casey argued that such a pact would be a stabilising factor in the Pacific and a check to Japanese activities and urged that a cablegram be sent to the U.K. Government suggesting that the French Government be pressed to make the necessary concessions. A fortnight later Menzies received circular dispatch B83 (sent 13 December 1939, received 3 January 1940) from the U.K. Dominions Secretary, Anthony Eden. Eden enclosed a copy of the draft Anglo- Thai pact of non-aggression sent to Crosby and asked the Commonwealth Government to forward as soon as possible any observations it might have to make. This dispatch was forwarded to the Department of External Affairs. All the above documents are on file AA: A981, Thailand 33.]
With further reference to your letter of 22nd December, 1939 , regarding the foreign policy of Thailand, you will, I think, be interested to know that, as a result of a suggestion made by the Minister for Supply and Development to the British Minister at Bangkok when they met there in December, the Minister is now sending copies of his principal despatches to the Foreign Office to me. This is a useful innovation which means that our information about Thailand is much more up-to-date.
I have now considered a recent despatch from the Secretary of State for Dominion Affairs concerning the proposal that Thailand should conclude non-aggression pacts with France and the United Kingdom. The position is that both the French and United Kingdom Governments have informed the Thai Government of their readiness to conclude such pacts. The United Kingdom Government has already communicated to the Minister at Bangkok a draft agreement which is based on a draft prepared by the French Government.
It appears that the refusal of the French Government to consider a request by the Thai Government that the thalweg of the Mekong River be adopted as the frontier between Indo-China and Thailand, involving a surrender of certain territory by France, may render the conclusion of a non-aggression pact between France and Thailand impossible although this is not necessarily so.
The United Kingdom Government wishes the Commonwealth Government to send any observations it has to offer on the draft pact by telegram and, after considering the draft pact and the information at my disposal, I suggest that a telegram might be sent to the Secretary of State for Dominion Affairs in the following terms:-
'Thailand. Your circular despatch B.No.83 of 13th December, 1939.
Commonwealth Government would welcome conclusion of non-aggression pacts between United Kingdom, France and Thailand on lines of draft submitted by your Government to Thai Government. In the event of conclusion of a pact between France and Thailand proving impossible, it hopes that your Government would still be able to conclude such a pact with the Thai Government.' 
I return herewith the original letter from Mr. Casey to yourself and its enclosure  which you kindly sent to me with your earlier letter.
[H. S. GULLETT]