The benchmark index surged 2.07 percent to a record 1,216.10 points on April 1, breaking the 2018 high of 1,204 points.
It then closed at 1,224.45 the next day. It had previously risen above 1200 on January 13 and 18 and March 18 this year.
But on the two occasions in January the index could not hold as investors offloaded large-cap stocks to take profits. On March 18 it hovered around the 1,190 mark throughout the day before a surge at close helped it close at 1,200.94. The next day it closed at 1,194.
On April 1, the index rose steadily, surging past the 2018 peak in the morning and continuing to rise until close to end with a near 25-point gain.
The upward trend continued on April 2 though system errors kept the gain low.
On the three earlier occasions the index was driven by mid-cap and penny stocks, but last week large caps were responsible, especially bank stocks, which indicates it could be sustained, according to Nguyen The Minh, head of retail research at securities firm Yuanta.
"To know for sure that the index has really surpassed the 2018 historical peak or if it is just a temporary rise before it falls again, we need to watch it for another one or two sessions."
The morning session would be decisive since the overload problem continues at the Ho Chi Minh Stock Exchange, he said.
Le Thu Hang, head of the investment advisory department at FPT Securities, said: "The VN-Index has thrice failed to remain above 1,200 points this year. Many investors played it safe by selling stocks when they were still at a high price."
However, in the last two sessions there was still high demand for stocks despite high prices, and so selling pressure is expected to be less this time, she said.
Hang said the VN-Index could hit 1,351-1,400 points this year.
Most securities firms expect the index to keep rising.
Bao Viet Securities JSC (BVSC) expected the gain to continue, though with corrections since some stocks are overbought.
It said the next resistance zone is at 1,235-1,250.
MB Securities, which too expected the index to keep rising, said: "If there are any fluctuations, it will be caused by investors restructuring their investment portfolio to invest in leading stocks."