As a unit of distance, 哩 is the English mile (about 1.6 km), distinct from the Chinese 里 (about 0.5 km). As a sentence-final particle it is read li, a dialectal variant of 呢 common in southern speech.
register
A third reading, lí, appears in the food word 咖哩 (curry), an older spelling of 咖喱. You will also see the character doubled as lī in the brand name 哔哩哔哩 (Bilibili).
Left radical 口, a small open square, here flagging that 哩 is a sound coming from the mouth: a sentence-final particle in dialect speech. Same use of 口 in particles like 吗, 呢, 啊, 吧, 啦, wherever Chinese needs a written marker for spoken-only flavour.
Right phonetic 里 supplies the sound (lǐ, no drift) and bleeds the meaning mile into 哩 when it is borrowed for the English mile unit. Same phonetic appears in 理 (reason), 鲤 (carp), 厘 (a hundredth).
