French neutrality and Russian refit in 1905

Could Russia hold support ships and destroyers in French Indochina for training and refit before Tsushima?

Only by breaking French neutrality, which could bring Britain into Japan's war against France.

Allowing training and repair over several months would exceed ordinary neutral hospitality. The arrangement would amount to material support for Russia. Japan could then treat France as an enemy, with Britain likely to back that response. A basing concession could collapse the distinction between neutrality and belligerence and widen the war.