Citizenship at birth where both parents are Bhutanese
No jus soli. Birth citizenship requires both parents to be Bhutanese citizens (1985 Act art. 2; Constitution art. 6.1). The only territorial category is registration for persons domiciled in Bhutan on or before 31 December 1958 (Act art. 3 / Constitution art. 6.2).
Sources: Bhutan Citizenship Act 1985, National Assembly PDF (Wayback of nab.gov.bt) ยท Bhutan Citizenship Act 1985, National Assembly (original URL; site often unreachable)