Group 2 is the unpaired low consonants — the sonorantsi: nasalsi (ม, น, ณ, ง), liquidsi (ร, ล, ฬ) and glidesi (ย, ญ, ว). They have no high-class twin. Thai's workaround, which you'll meet in the tone rules, is to put a silent ห in front of them (หมู, หนู, แหวน) to make them behave as high class. Several of the name-words below already use that trick — the transliteration shows you the tone it produces.
Every Thai consonant has a two-part name: its sound plus a word that starts with it — like saying “A for Apple.” So ก is gaw gài: “gaw” is the sound, ไก่gài means chicken. Tap a card to hear the full name, or the pill to hear just the word.