I can’t found some alphabet with some diacritics

are they not commonly used? Why there is no vowel with the caron? But there are “č” “š” .

as Thai who wanna romanised Thai language using diacritics because of the tones. But there is no vowels with caron in keyboard for the rising tones. Only à á â ä æ ã å ā that available. Why? It may not using in writing but there using as phonetic alphabet.