It is clear that in today's time all those who are Muslims irrespective of sects really believe Muhammad (pbuh) as a prophet hence they can't be the kind of Munafiq(Hypocrite or double-crosser) at the time of the Prophet (pbuh). But we also find such instances during the life of Prophet (pbuh) of companions who also believed in the Prophet (pbuh) by their hearts but became a bit lazy and did not go to Jihad which caused their boycott, accused Prophet (pbuh) of unfair war spoil distribution etc.They were found not to be hypocrites like the other hypocrites who just showed off their belief in Muhammad (pbuh) but only erred and disobeyed some commands of the Prophet (pbuh) (say like not going to Jihad). So even in the current time, is it possible for a person to become Munafiq while believing in Muhammad (pbuh) as a Messenger?
It is a very good and important question, as any one can get the feeling anytime in his life that either he himself, or his nearby believers may seem to be doing things only to be seen.
We should remember that there is a thin line between perfect belief and Hypocrisy.
Transition: Belief -> Heedlessness(believe but do not follow) -> Disbelief.
Belief: Persists because of fear from Allah and the hereafter and are cautious about it.
Heedlessness: Affirm the fact that there is something called hereafter, but are not cautious about it due to laziness.
Indeed, the hypocrites [think to] deceive Allah , but He is deceiving them. And when they stand for prayer, they stand lazily, showing [themselves to] the people and not remembering Allah except a little, (Qur'an 4:142)
Disbelief: The fear of hereafter is negligible or NIL that they do deeds ONLY to be seen.
Have you seen the one who denies the Recompense?(Qur'an 107:1)
So woe to those who pray, [But] who are heedless of their prayer - Those who make show [of their deeds] (Qur'an 107:4-6)
After all these are the ill effects of our Cursed enemy Shaitan. So anyone can fall prey to this and should be careful. We must remember Allah in abundance so that he may guide us to the straight path.
May the creator guide us all.
Hypocrisy as a definition means saying one thing and doing another. It does not mean not believing in Allah. You can be a hypocrite and still believe in Allah and you can be a hypocrite and not believe in Allah (like some during the time of the prophet PBUH). It was narrated:
"The signs of the hypocrite are three: when he speaks he lies, when he promises he breaks his promise and when he is entrusted he betrays the trust." (Bukhari and Muslim)
This clearly shows us that you can be a Muslim and a hypocrite. Being a hypocrite does not automatically remove you from being a Muslim as we all know there were many Sahaba that were hypocrite yet still believed in Allah (like those mentioned in the Quran who made up excuses to avoid going to Jihad):
“And those who made excuses from the Bedouins came (to you, O Prophet) asking your permission to exempt them (from the battle), and those who had lied to Allah and His Messenger sat at home (without asking the permission for it); a painful torment will seize those of them who disbelieve” [al-Taubah 9:90]
There are some scholars who break Nifaq (Hypocrisy) into 2 sections (Greater, which does with disbelieve and lower which deals with the above mentioned Hadith), a distinction never made by the Prophet PBUH.
First discussion about hypocrisy in the Qur'an can be found in earlier parts of Surah al-Baqara.
وَمِنَ النَّاسِ مَن يَقُولُ آمَنَّا بِاللَّهِ وَبِالْيَوْمِ الْآخِرِ وَمَا هُم بِمُؤْمِنِينَ
And of the people are some who say, "We believe in Allah and the Last Day," but they are not believers.
As indicated by the ayah, hypocrites are people who claim to belive, but they are actually not believing. They try to blend in with believers, and they say that "we believe in Allah and the last day too". As indicated by following ayah, these people are the kind of hypocrites that are aware of their actions.
يُخَادِعُونَ اللَّهَ وَالَّذِينَ آمَنُوا وَمَا يَخْدَعُونَ إِلَّا أَنفُسَهُمْ وَمَا يَشْعُرُونَ
This ayah mentions that, they make an effort to decieve. So this kind of Hypocrites know what they are doing.
There is also another kind of Hypocrites, who follow the religion when it is convenient for them and they don't follow the religion when it is not convenient.
وَإِذَا قِيلَ لَهُمْ آمِنُوا كَمَا آمَنَ النَّاسُ قَالُوا أَنُؤْمِنُ كَمَا آمَنَ السُّفَهَاءُ ۗ أَلَا إِنَّهُمْ هُمُ السُّفَهَاءُ وَلَٰكِن لَّا يَعْلَمُونَ
And when it is said to them, "Believe as the people have believed," they say, "Should we believe as the foolish have believed?" Unquestionably, it is they who are the foolish, but they know [it] not.
This is the dangerous kind of hypocrisy as those people don't know that they are munafiqs.
There's actually 2 types of hypocrisy the one that makes you an infidel as if you proclaim being a Muslim and deep down your heart you're not that's one thing; As for the other type is actually very common and an honest person would ask himself whenever he's doing anything in life, am I doing this for the sole purpose of pleasing GOD? Am I doing this (prayer charity .. ) for a materialistic benefit (money, others praising ..) ? this is actually a journey that we all should take towards enlightenment and purification to the point were everything we do is only to please GOD to quest the high virtues and morals. Your question is an excellent start.