'Thai orthography' option turns all anusvaras/candrabindus of a̅, i, and au to ṅ regardless of the varga the following consonant belongs to.

[saris-a37]

The 'Thai orthography' option does not properly convert anusvaras/candrabindus to nasals. This happens only to some vowels.

what the result should be: anusvaras/candrabindus of all vowels in this example should turn to ณ (ण ṇ) since they're all followed by ฑ (ड ḍ), a retroflex consonant
what really happens: anusvaras/candrabindus of -า (ा a̅), -ิ (ि i), and เ-า (ौ au) turn to ง (ङ ṅ) as seen in the second, third, and the last line; all other vowels work fine though.

Thanks.