On 6 March 1589 he was nominated by the Privy Council as one of three people for maintaining the true religion in the Forest and Tweeddale, and was settled at Selkirk.

[7] Although Welsh did not arrive in Aberdeen until two days after the July 1605 General Assembly had been held, he was ordered to become a ward or prisoner in Blackness Castle.

Shortly afterwards he became the pastors of the Protestant churches of Nerac, Jonsac, and eventually Saint-Jean-d'Angély in Saintonge, where he remained for sixteen years.

The town council of Ayr continued to regularly remit his stipend as minister of the parish to him for several years after his banishment.

[7] When Saint-Jean-d'Angély, a strongly fortified town, was besieged by King Louis XIII during the war against the Protestants in 1620, Welsh encouraged the citizens to form a resistance and helped operate the guns on the walls.

After the town surrendered, he continued to preach as usual until he was summoned before the king, who reprimanded him for violating the law forbidding anyone from providing religious services other than the standard.

When the town was captured again in the following year, the king ordered guards to be placed around the house of Welch and provided horses and wagons to convey him, his family, and his household goods to Rochelle in safety.

Through John Young, Dean of Winchester, an attempt was unsuccessfully made to obtain a general approval of episcopacy from Welsh.