i'm a solo thief and having a heck of a time killing him. any advice would be much appreciated, i currently use daystar and and flame tongue or the tuigan bow. please help

Um, of COURSE you're having a heck of a time beating him.. There are ways to get around fighting the Shadow and Red dragons because entire PARTIES have a heck of a time beating them.. I'm sorry (or not) but unless you cheat and hack, I don't know if a solo thief can do it.. Do you have ToB installed? Maybe setting traps everywhere and the Use Any Item feat might help.. Then you could use scrolls of Time Stop and summoning all sorts of beasties.. But I've never dared try it on my own without being an epic-level char.
Maybe, just for this one fight, you might consider bringing some others along. Edwin and Jahiera come to mind, as they can summon monsters. Wands of Monster Summoning also come to mind.. Although if the dragon is immune to normal weapons it's mostly useless (Though you could hang back and shoot arrows while the Shady takes out the beasties.) But seriously, do consider bringing others along for the fight. The fight will be a challenge for a seasoned party.. One thief alone is dragon food.

solo thief, so no party, but are you a theif kit, or a straight thief? and what lvl? if you have set traps, I'd recommend that cheesy yes, but as a theif you prbably don't have alot of other firepower, not nearly as good a Thac0 as a fighter, and no spells, lay traps use potion of speed, and run/snipe... if you have UAI you can use the wand of fodder(monster) summoning to provide you a few shots in peace, not many tho...

i'm lvl 17 and right now i'm considering bringing someone in to help. i don't have TOB and i'm playing a straight thief proficent with long swords.

alright i just killed the beast. i had to ask Nalia to help, she first cast feeblemind on the beast and then i hacked away and the beast soon fell. hmmmm, almost solo but needed her help. after all she owed it to me i cleared her keep for her.

A bit cheezy method that could allow you to be a bit "more solo" next time. Take Yoshimo to the dragon. Now:
1. Let Yoshimo set all his snares.
2. Pretend to dismiss Yoshimo. Tell Yoshimo that you are joking when Yoshimo asks you whether he should really leave. Because of a bug in the game, Yoshimo gets back all his snares, therefore, he can lay next ones.
3. Repeat until you have enough snares around the dragon.
4. Dismiss Yoshimo - be serious with it this time.
5. Trigger the dragon.
I've never tried it but I've heard that it works.

My solo Assassin used Traps... poor Dragon never knew what hit him... ...