Altering a dress using pins?

I had a dress like that several years ago. I bought a roll of double sided "body tape" online. You stick it to your body and then press the material to the tape. It did a great job.

Definitely body tape if you cannot find it online look for tit tape as that is what it’s called in the fashion industry 🤗

You could permanently fix with a fine needle and thread and carefully sew but otherwise "Tit tape", as the other GNers said is your answer.

I wear a camisole underneath one that is too low.

Great information ladies, thank you. I shall order some now.
It has given me a laugh too. Looking forward to a good night’s sleep.

You can buy modesty panels that fix onto your bra and you can adjust how low or high you wear them.
I have just had to buy some as I am going to Japan to demonstrate crafts and have been informed that my v-neck dresses which are not at all riske in this country may not be suitable over there.

Modesty panel sounds very Victorian!

Wow would be very afraid of putting tit tape on search engines. With all the porn these days would most likely get police knocking 🙄

If you decide to sew can I suggest using hair rather than thread as it is much finer though probably stronger, (obviously it requires access to someone with long hair in the required shade) 😬

You could spray it with starch then sew it, then wash it to take the starch back out.

Body tape should work, half the dancers, tv stars you see with revealing clothes use it.

This has just reminded me that we used to sew up holes in our tights with hair at school!

I had forgotten about sewing with hair. Grey dress and grey hair. Thank you all again.