The /θ/ sound is spelled with <th>. The /l/ sound is spelled with <l> or <ll>.
This is a contrast between a voiceless dental and alveolar fricative and a voiced lateral continuant, fairly close together in the mouth. It is not a problem, although the sound /θ/ is difficult for many learners.
One interesting oair is thicker/liquor.Since the /θ/ sound is of low frequency overall, the mean density value is low at 0.6%. The list makes 56 semantic distinctions, a loading of 72%.
both bole death dell deaths dells doth dull earth earl earthy early earthier earlier earthiest earliest faith fail forth fall fourth fall fourths falls fourths false firth furl firths furls girth girl hath Hal heath heal heaths heals heath heel heaths heels Keith keel kith kill Meath meal moth moll myth mill 'neath kneel 'neath Neil Perth Pearl pith pill ruth rule saith cell saith sell sheathed shield teeth teal thane lain thane lane thanes lanes thank lank thatch latch thatched latched thatches latches thatching latching thaw law thaws laws thaw lore thawed laud thawed lord theft left Theo Leo thick lick thicker liquor thief leaf thigh lie thighs lies things lings think link thinking linking thinks links thong long thongs longs Thor law Thor lore thorn lawn thorns lawns thug lug thugs lugs thump lump thumped lumped thumping lumping thumps lumps tooth tool troth troll withe will worth whirl wraith rail wraiths rails wroth rôle