May be involved in the salvage of thiamine breakdown products (PubMed:25014715). This protein has a haloacid dehalogenase family domain fused to its TenA domain (PubMed:25014715). Phosphatase with the highest activity against thiamine monophosphate (ThMP) and, with a lower activity, against thiamine diphosphate (ThDP), flavin mononucleotide, inorganic pyrophosphate, CTP and dATP (PubMed:27677881). Has a thiamine salvage hydrolase activity, but only against 4-amino-5-aminomethyl-2-methylpyrimidine (amino-HMP) and not against N-formylamino-HMP, desthiothiamine, thiamine, ThMP, and ThDP (PubMed:27677881). H2O + thiamine phosphate = phosphate + thiamine 4-amino-5-aminomethyl-2-methylpyrimidine + H2O = 4-amino-5-hydroxymethyl-2-methylpyrimidine + NH4(+) kcat is 13.5 sec(-1) for thiamine monophosphate. Localized to the mitochondrion when the first start codon is preceded by a strong Kozak sequence. The thiamine monophosphate phosphatase activity resides in the HAD domain (297-571), while the TenA domain (85-292) has thiamine salvage hydrolase activity (PubMed:27677881). Knockdown mutants show reductions in root length and shoot growth. In the N-terminal section; belongs to the TenA family. In the C-terminal section; belongs to the HAD-like hydrolase superfamily. Extended N-terminus. Truncated N-terminus.