Montana status as a resident can’t be lost until residency in another state or country is gained.
Mont. Code Ann. § 1-1-215(3).
Foreign Earned Income Exclusion = Yes
Foreign Tax Credits = Yes
Treaty = No
Due Date = April 15
Accepts Federal Extensions = No extension is required when 90% or more of the tax payable has been paid. If there is a balance, file form EXT-13