coming from someone who has worked both as a nanny and nursery teacher/head mistress for 20 years mainly with 2-5's, living in an environment as yours is with the uncertainty of how your mum will react to your son is definitely going to affect his behaviour, he needs consistency in his home life to feel safe and loved. I understand you can do little about your mums behaviour, but you can make your bedroom a safe zone, i would try putting him in your bedroom (not on his bed or he will associate bed time as punishment) as soon as the tantrum starts, tell him you are putting him in there because his behaviour is upsetting you and he can come out when he is ready to be nice again. close the door and stand outside it, holding it closed if necessary. that way other family members can not interfere with your actions. your son will learn that having tantrums leads to being excluded from things and upsets people, these are the two things which children do not want to do. their aim in life at two is to be as nosy as possible and be liked by everyone. so he will soon learn that to achieve these he has to stop the tantrums.
two year old tantrums are normal, biting and kicking are pretty common through these. it is how you deal with these actions that will determin how many times they occur. there is nothing wrong in telling your son he will not be allowed to go to a friends or the park that afternoon because he bit you as long as you keep to this, i personally would drum it home too by every so often during the afternoon telling him ..do you realise if you had not bit mummy this morning you could have been playing with ...now! it works believe me i did it once, that is all it took!
another one is to not read a bed time story, but sit there with him reminding him that there is no story because he bit you, he will probably kick off, but simpply walk out and stand behind the closed door till he calms down then simply go in and kiss him good night before going out again.
you have to be consistent and follow through with everything so if family are not willing to stick to what you say to him then you have to find pleasurable things you can stop which they can not interfere with or be on guard to stop them interfereing when you are following through a punishment.
do not get stuck in the trap of only acknowledgeing the bad behaviour, you need to balance that with rewarding the good behaviours too. rewards can be a cuddle, your time/attention or a sticker on a chart.
a star chart may be just the job for him, get a piece of plain paper, a coloured felt pen and some blu tack, sit him down with you, explain that whenever he has a tantrum it makes you feel bad, you do not like feeling bad, so for every night that he does not make you feel bad you will draw a star on the paper for him, and when he has three stars you will take him to the park or whatever you deem a good reward (not a new item or sweets) then ask him where you should stick the paper so you can both see it and do so together. remind him of the chart when you come home each night.. remember there has to be no tantrums tonight if you want mummy to draw your star. when he has three stars follow up with the reward, make a big thing of it, tell the rest of the family what you are going to do, let him show them his three stars on the chart, phone uncle whoever in tiland, take the star chart to nursery to show his teacher whatever but make out like its the best thing ever as this will really make him feel proud of his achievement even if it took 6 weeks to get three stars still make a big thing of it. then make the next reward when he reaches 5stars, then 10 etc till he no longer relies on the chart to be good! this works really well if followed through properly and because he only gets a star when you draw it in your 'special pen' others can't interfere with it if you keep the pen safe.