He studied at a theological seminary in Pinsk, a gymnasium in Libava (now Liepaja, Latvia) and later at the Riga Technical University.

During the 1905 Russian Revolution, Ułasaŭ organised workers' strikes in various Belarusian cities, participated in an illegal teachers' convention.

For his social and political activities and publications Ułasaŭ was sentenced by the Russian authorities to 4 months of imprisonment in 1909.

In December 1917, Ułasaŭ took part in the First All-Belarusian Congress and in 1918, became a member of the Rada of the Belarusian Democratic Republic.

[3][4] At the time of the conclusion of the Polish-Russian Treaty of Riga in 1920, Ułasaŭ lived in Radaškovičy, which ended up in the territory of the Second Polish Republic.